Tap switch



May 9, 1944. R, H QLSQN 2,348,222

TAP SWITCH Filed 0G12. 2, 1942 Patented May 9, 1944 TAP SWITCH Roy H. Olson, Marion, Iowa, assigner to Collins Radio Company, a corporation of Iowa Application October 2, 1942, Serial No. 460,559

(Cl. 20o-11) 7 Claims.

This invention relates to a tap switch, and more particularly to a switch operating on the same general principle as a fan switch,- but having its taps arranged around a center in an arc exceeding a semicircle.

One feature of the invention" is that it enables an arrangement of the taps in an arc approaching a full circle; another feature of this invention is that it enables unused portions of the element connected to the taps to be shorted despite the fact that the contact arc is greater than a semicircle; yet another feature of this invention is that it enables a given number of taps to be arranged in an arc of smaller radius, or with greater spacing between taps, highly desirable in transmitting equipment Where high voltages are being handled; other features and advantages of this invention will be apparent from the following specification and the drawing, in which:

Figure 1 is a side elevational view of a switch embodying this invention; Figure 2 is a view along the line 2, at right angles to the view of Figure l; Figure 3 is a view similar to Figure 2, but with the contact arms rotated somewhat, this view showing one of the contact arms moving up an incline leading from one plane of rotation to a different plane of rotation; Figure 4 is a sectional view along the line 4 of Figure 1; Figure 5 is a fragmentary detailed view showing the inclined portion of the displacement member, the other portion being broken away; Figure 6 is a schematic diagram of the operation of the device shown; and Figure 7 is a schematic diagram illustrating the principle of operation of a switch of this type.

Certain electrical elements are frequently associated with a tap switch for varying the amount -or portion of said element which is active in the circuit to which it is connected. One example of this is an inductance coil in radio apparatus, either transmitting or receiving, such a coil being frequently associated with a tap switch to enable its inductance to be varied, in steps, from minimum to maximum. Since the unused portion of the coil has distributed capacity, it is necessary at higher frequencies to short the unused or inactive portion of the coil. Moreover, this shorting cannot be done at higher frequencies by a mere connection across the entire unused or inactive portion since the points of shorting connection must be close enough together to prevent self-resonance at the frequencies being handled. f 4

Means for properly shorting parts of the inactive portion of the coil as the active portion is coil I0 is shown having its ends connected by leads Il and I2 to some other circuit element with which it cooperates, as for example, a condenser. 'Iaps i3d-i are provided, these being connected to thev coil at equally spaced points; and switch members |4a-i are adapted to cooperate with these taps. These switch members I4 are interconnected mechanically and electrically, as is indicated schematically, and movement of the switch member assembly upwards (speaking with respect to the position of the parts shown in Figure 7) step-by-step results in varying the portion of the coil while maintaining the inactive portion shorted with connections suniciently close together to prevent any difficulties with self-resonance even at high frequencies. For example, if the switch member assembly is moved up two steps until switch member Ma engages tap I 3c, it will be seen that that portion of the coil 1ying between |3a and I3c will be active in the circuit, While the remaining portion lying between |3c and I3i will be inactive and shorted at a plurality of points.

While this arrangement is very satisfactory from an electrical standpoint, its embodiment in actual switch structure has heretofore been limited to apparatus where the taps were arranged around the center in an arc not exceeding a semicircle, since the contact arms had to have an inactive arc, to which they could move, equal in size to the arc in which they werearranged. 'I'his space limitation resulted in unduly limiting the number of taps which could be used, or requiring an arc of excessively large radius. The present invention obviates this diiculty and enables the taps and contact arms to be arranged in an arc closely approaching a full circle, so that the same number of taps with the same spacing can be arranged in a circle of about half the dameter of that heretofore required.

Referring now more particularly to Figures 1-5, a coil I5 is shown having a tap switch associated therewith at one end. Taps ISa-i are arranged about a center coaxial with the shaft I 1, the upper or contacting surfaces of the taps lying in a plane and in an arc closely approaching a full circle, this arc being considered as having one end starting at IBa and as having its other or terminal end at |61'. The taps are electrically connected in conventional manner to the turns of the coil at similarly spaced intervals, as shown ln Figure 1.

active f A switching arrangement is carried by and rotatable with the shaft I1, this arrangement including switch arms Isa-e, these being shown in Figure 2 as having their contacting tips in the same plane as the surfaces of the taps i8, the arms being so arranged as to contact every other tap. It will be understood that this is a matter of choice, the number of taps being determined by the number of steps of inductance which are desired and the number of taps between switch arms being determined by the amount of coil which can be bridged before selfresonance takes place at the frequencies being handled. In order to keep one end of the coil always connected to the circuit regardless of the position of the switch arms, variation taking place at the other end of the coil, tap |61' is connected by a strip i9 to the contact ring 20 engaged by brushes 2 la-c, electrically and mechanically connected to the switch members.

As may be best seen in Figures 2-5, the nsulatiug member 22 in which the taps are mounted serves not only as a bushing for the shaft l1 but also as means for supporting a displacement member 23, this member having an inclined portion 23a and a plane portion 23h which is concentric with the shaft I1 and in a plane parallel to but spaced from that of the contacting surfaces of the taps. The displacement member 23 is mechanically attached to the member 22 in any convenient means, but with the point of attachment or support outside of the arc in which the contact arms i8 move, as may be best seen in Figure 4.

When the switch arms are in the position shown in Figure 2, they coincide with the arrangement schematically shown in Figure 6, all of the coil being shorted out and none of it being active. When it is desired to render part of the coil active, the shaft l1 is rotated clockwise (speaking with respect to the parts as shown in the drawing), as by the knob 24. A rotation of approximately 90 brings the parts into the position shown in Figure 3, where the arm |8e is shown as having passed up the inclined portion 23a and now riding on the upper surface of the portion 23h of the displacement member, the arm lad being shown moving up the inclined portion. This view was chosen to illustrate the way in which the contact arms move from the contact plane to the displaced plane, but it will b'understood that rotation will be continued until the contact arms stop on a desired tap, as for example, with the arm 18a on the tap iSd, when the portion of the coil between the taps Isa and iSd would be active. The displacement is pcssible, of course, because of fiexibility in the spring metal arms i8; and it will be apparent that it is only by moving these arms to a different plane that they can be caused to pass over part of the tap arc without causing undesired effects. If it were not for this displacement, for example, when arm lBa was on tap iSd, arm iSd would be on tap IEa, and none of the coil would-be active. The inclined portion must lie in the space between the ends of the arc in which lthe taps are arranged, and the size of this space and the amount of space between the two planes is determined by the voltages to be handed and the possibility of arcing difficulty, just as this same factor determines the permissible spacing between the taps.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes. therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

`I claim:

1. A switch of the character described, including: a set of ,contact members arranged around a center in an arc exceeding a semicircle; another set of contact members arranged around said center and adapted to make engagement with the members of the other set; means for rotating one of said sets with respect to the other; and means for moving at least some of said members to and maintaining them in a different plane during said rotation.

2. A switch of the character described, including: a set of separate contact members arranged around a center in an are exceeding a semicircle; another set of contact members arranged around `said center, this set being interconnected and adapted to make engagement with the members of the other set; means for rotating one of said sets with respect to the other; and means for moving at least some of said members to a different piane during said rotation.

3. A switch of the character described, including: a set of contact members having their contacting surfaces in a plane and arranged around a center in an arc exceeding a semicircle; a set of cooperating contact members having their contacting surfaces in said plane and arranged around said center; means for rotating one of said sets with respect to the other; and means for moving at least some of said contacting surfaces out of said plane during said rotation.

4. A switch of the character described, including: a set of contact members having their contacting surfaces in a plane and arranged around a center in an arc exceeding a semicircle; a set of interconnected contact arms having contacting surfaces arranged in the same plane and arc; means for rotating the arms around said center; and means for moving the contacting surfaces on said arms out of said plane when the rotation would otherwise cause undesired contacts.

5. Apparatus of the character claimed in claim 1, wherein the last mentioned means is operative on a contact after it has left one end of said arc and before it reaches the other end.

6. Apparatus of the character claimed in claim 4, wherein the last mentioned means comprises a member having a portion in a 'plane spaced from but parallel to the first mentioned plane and an inclined portion leading from one plane to the other.

7. A switch of the character described, including: a plurality of taps having their contacting surfaces in a plane and arranged around a center in an arc exceeding a semicircle but less than a full circle; a set of interconnected contact arms having their tips arranged at the same distance from said center as said surfaces and movable in the same plane; means for rotating the arms around said center; and a member having a portion overlying said taps in a plane spaced from but parallel to the first mentioned plane and an inclined portion leading from one plane to the other, this portion being in the space between the ends of said arc, whereby rotation of said tips causes them to move from one plane to the other after leaving one end of said arc.

ROY H. OLSON. 

